Electric hammer



A. G. DECKER ELECTRIC HAMMER Jan. 5,

Filed Aug. 14, 1926 2 Sheets-Sheet l 00000 0 JIEJGEBO 000000 am, 5, 1%32. G, DECKER 1,839,743

ELECTRIC HAMMER Filed Aug. 14, H26 2 Sheets-Sheet 2 Patented Jan. 5, 1932 UNITED STATES PATENT OFFICE ALONZO G. DECKER, OF BALTIMORE COUNTY, MARYLAND, ASSIGNOB TO THE BLACK d:

DECKER MANUFACTURING COMPANY, OF

MARYLAND TOWSON, MARYLAND, A CORPORATION OF ELECTRIC HAMMER Application filed August 14, 1926. Serial No. 129,248.

The invention relates to portable power driven hammers and more particularly to the type of hammer which is best adapted for use with an electric or similar drive in that it relates essentially to the transformation of the high speed motion of an electric motor into a series of comparatively infrequent hammer blows.

In the operation of power driven hammers of the type just identified, the shocks 0r v1- brations due to the reactions of the hammer blows transmitted backward through the train of gearing to the motor is an important source of failure. The most fre uent effects of these harmful stresses appear in the form of loosening of the pinion on the armature shaft or failure of the shaft, but in less frequent instances they are manifest in other ways. The difficult has been overcome in the present instance y the introduction of a resilient element into the drive between the motor and the hammer.

In the preferred form of the invention illustrated, this resilient element is in the form of a helical spring by which two gears or rotary members, which may be on the same axis or shaft, are connected together for transmission of rotary motion and power from one to the other, the resiliency of the .spring serving to take up and equalize the I the invention in the preferred form.

In the drawings: I

Figure 1 is a side elevation of a complete portable power driven tool of thls type lookmg in the direction of the hammer axls, showing the casing closed.

Figure 2 is a similar view broken away for convenience and with the cover removed and showing the outline of the hammer member, gears, etc. Figure 3 is an enlarged section through the casing on the line 3-3. in Figure 2, the gears, hammer, etc., being shown in eleyation, the lower part of the casing or extenslon thereof carrying the anvil being also broken away.

Figure 4 is a section on the line 44 in F ig ure 3.

Referring to the drawings by numerals,

each of which is used to indicate the same or similar parts in the different figures, the portable power driven hammer illustrated includes a motor 1 which in the form of the invention shown is an electric motor enclosed in a casing 2 to which is attached at one axial end a handle 3 carrying a switch lever 4. The grip 5 of this handle may be utilized as a switch casing. The handle portion also includes a casing section 6 which encloses the commutator, brushes and connections, not shown." Secured to the other end of the motor cas-- ing or housing 1 is a gear casing 7 which encloses the gears, shafts, etc., comprising the means for transforming the rotary motion of the motor into impulses or blows, i. e., the hammering mechanism to be described. The lower end of the casing is provided with an extension 8 in the general direction of the axis thereof shown as slightly oifset therefrom which is provided with suitable slide bearings 9 for the anvil 10.

More specifically the hammering mechanism comprises a beveled pinion 12 secured to the motor shaft 14 and meshing with a beveled gear 15 which may be supported for rotation in any suitable manner. In the construction shown it is secured to the shaft 16 intersecting the line of the shaft 14 at right angles. The shaft 16 is mounted in suitable bearings 17 in the casing and a spur toothed pinion 18, as shown, is carried by the shaft at one side of the casing, the spur pinion having a free running fit relative to the shaft and belng permitted to oscillate relatively thereto.

In the form of the invention illustrated this spur pinion 18 is connected with beveled pinion 15 by the flexible connection 19. In the preferred form this flexible connection consists of a coiled spring or helical spring 19 having one end 20 seated in or secured to the beveled pinion 15 and the other end 21 seated in or'secured to the spur toothed pinion 18. This connection provides for a high degree of flexibility in the nature of a rotary yielding of the pinion 18 relatively to the beveled pinion 15 and serves to take up and equalize and eliminate all harmful effects on the gearing, shafts, etc., of all shocks and vibrations transmitted backwardl from the hammer through the gears, sha ts, etc., to the motor, as hereinafter described.

As shown in the drawings the spur pinion 18 meshes with a comparatively large spur gear 23 which is mounted in suitable bearings 22, 24, at the sides of the casing. This spur gear 23 is provided with a projecting hub 25 which is comparatively lon and of a diameter slightly less than that o the gear. This hub is cut away as illustrated forming a cavity or chamber 26 to receive the hammer member 27 which in the form of the invention illustrated is of the centrifugal type. This hammer member is pivotally mounted on the hub 25 eccentrically of the gear 23, the hammcr shaft being indicated by reference character 28. This shaft has bearings 29 in the hub 25 and gear member 23 at each side of the cavity 26.

The upper end 30 of the anvil, as illustrated particularly in Figure 4, is supported adjacenttheciroumferenceof the hub 25 preferably, as shown, just below the center and at one side. The impulses or hammer blows are produced by the action of the hammer member 27 which is of an extreme radius equal to or slightly less than the distance from the center of the hammer shaft 28 to the circumference of the hub 25 where this distance is greatest, this point being at X at the right in the form and position of the tool illustrated in Figure 2. As the hub and gear rotate the hammer member 27 is swung ontwardly by centrifugal force to the position which it occupies in Figures 2 and 4, the path indicated intersecting the top of the anvil. Contact of the hammer with the anvil gives a blow due to the mass and speed of the hammer and produces a reaction or rebound which swings the hammer to the right as seen in Figure 2, in which position its outer circumference is withdrawn within the hub 25 and before it can recover it has passed the anvil, the centrifugal force generated by rotation of gear 23 and hub 25 bringing the hammer to striking position before the revolution is completed, resulting in another blow on the anvil as the parts reach initial position.

It is apparent that in the absence of a flexible connection the intensity of the repeated shocks or vibrations which must be withstood by the connections 12, 15, 16, 18, 23 correspond directly to the intensity of the hammering effect produced, and in the absence of some means for relieving the resulting stresses it is extremely difiicult, if not impossible, to produce a train of gears or power transmitting means from the motor to the hammer which is not excessively heavy and expensive and will stand the strain for any considerable erlo p The difficul ty involved has been overcome and a greatly improved product of an increased length of life has been produced by the provision of the resilient member introduced in the train of gearing between the motor and the hammer. The structure described with the various features and details also constitutes a new and improved application of a rotary electric motor to the production of hammer blows in and by a portable tool.

I have thus described specifically and in detail a power driven portable hammer involving the feature of my invention in the preferred form, however, the specific terms herein are used descriptively rather than in a limiting sense, the scope of the invention being defined in the claims.

What I claim and desire to secure ters Patent is:

1.- In a portable power driven hammer, a rotary electric motor having a shaft, a rotary member carrying an eccentrically mounted swinging hammer, an anvil to be engaged by the hammer as it swings from the rotary member, gearing connecting the motor shaft to the rotary member to drive the latter, said gearing comprising a beveled pinion on the motor shaft, a beveled gear driven thereby, a spur pinion driven from the boveled gear and and a spur gear carrying the said rotary member and driven from the spur pinion, the connection between the spur pinion and the beveled gear comprising a coil spring secured at its opposite ends to said respective beveled gear and spur pinion.

2. A portable electric hammer comprising a rotary electric motor having a shaft, :1 bevel pinion on the shaft, a bevel gear engaged thereby, a spur pinion driven from the bevel pinion, a spur gear of comparative large diameter driven at a reduced speed as compared to the motor, from and by the spur pinion, the spur gear having a hub, a hammer member eccentrically mounted on the hub to swing relatively thereto and of sufficient length to project therefrom when thrown out by centrifugal motion, an anvil in the path of the hammer when thus thrown out by centrifugal motion and a stop on the hub to check the rebound of the hammer in a position to pass the anvil and a resilient member between the hub and the motor to take up and equalize the shock due to the reaction of the hannner blow.

Signed by me at Towson, Maryland, this 26th day of July, 1926.

ALONZO G. DECKER.

by Lot 

